1. Field of the Invention
This invention relates to ink jet type recording apparatuses with nozzles for jetting ink droplets, and more particularly to an ink jet type recording apparatus with cleaning means for removing solidified ink, dust, fibers, etc. from the nozzle surface of the recording head.
2. Description of the Prior Art
In an ink jet type recording apparatus, a small quantity of ink is jetted, in the form of droplets, from the nozzles of the recording head by the energy produced by a piezo-electric oscillator or heat generating element, thus forming characters, patterns, etc. on a recording medium. The energy produced by the piezo-electric element or heat generating element to fly ink droplets is low, and therefore the gap between the nozzle surface and the recording medium is extremely small, not more than several millimeters. Hence, when colliding with the recording medium, the ink droplets are splashed back towards the recording head, thus sticking onto the nozzle surface. The ink droplets thus stuck attract fibers coming out of the recording medium and dust in the surrounding air to cause them to stick to the nozzle surface. The fibers and dust thus stuck may clog up the nozzle openings.
The recording head of ink jet type has a number of nozzles extremely small in diameter. Those nozzles are liable to be clogged up as was described above, and in addition they may be clogged up by the solvent of the ink itself. In order to overcome this difficulty, in general the ink jet type recording apparatus has a capping member for hermetically sealing the nozzles, and an ink discharge restoring function of applying negative pressure to the capping member to forcibly discharge ink from the nozzles. However, this ink discharge restoring operation suffers from a difficulty that ink discharged from the nozzles is splashed on the nozzle surface, so that, similarly as in the case where ink is splashed during printing, fibers coming out of the recording medium or dust in the air may stick to the nozzle surface.
In order to clean the nozzle surface which has been contaminated by ink splashed in various manners as was described above, the ink jet type recording apparatus has means for cleaning the nozzle surface.
For instance, Japanese Utility Patent Application (OPI) No. 5647/1986 (the term "OPI" as used herein means an "unexamined published application") has disclosed an ink jet type recording apparatus having a cleaning unit which comprises: a first cleaning member made of a porous plate such as a sponge; and a second cleaning member made of a rubber plate. The first and second cleaning members are arranged in such a manner that the front end portions of them are free with the rear end portions fixed, and the free front end portions are held protruded into the path of movement of the recording head.
With the apparatus, whenever the recording head is moved in one direction, the first cleaning member (porous plate) wetted with a solution rubs the nozzle surface of the recording head; and whenever the recording head is moved in the opposite direction, the second cleaning member scrapes the solution off the nozzle surface. Thus, the nozzle surface is maintained substantially clean at all times.
The size of those cleaning members is selected in compliance with the size of the nozzle surface of the ink jet type recording head; that is, it is considerably small. Hence, it is considerably difficult for them to have an elastic strength enough to provide a contact pressure required for cleaning the nozzle surface. That is, the above-described cleaning unit suffers from difficulties that, since the first and second cleaning members are fixed only at the rear ends, they are low in elasticity, and the solidified ink or fibers removed by the cleaning operation are liable to enter the gap between the first and second cleaning members.
U.S. Pat. No. 4,951,066 has disclosed a cleaning unit comprising a blade member of rubber, and a rubbing member made of a porous sheet which are both arranged outside of the printing region. The cleaning unit is advantageous in that those members are positively brought into elastic contact with the nozzle surface, so that the contaminants are positively wiped off and the solution is also positively scraped off; however, it is still disadvantageous in that it is rather intricate in construction because it needs means for driving the first and second cleaning mars.